It generally takes a few hours to do any of these ramp surveys. We do them by mounting a survey-grade GPS receiver and antenna on a vehicle, and driving a grid pattern. We've not published any details on our procedure.
We process the resulting GPS data much as we would an aircraft trajectory, although the results are better since we can use single-frequency approaches due to the short baselines involved. A key thing is to be extremely careful about measuring antenna heights with the vehicle loaded, and to account for phase center variations particular to the vehicle involved, since this is our primary technique for determining range biases, which we try very hard to keep well within 1 cm.
The processing for our ramp surveys is differential, with precise orbits and clocks on a very short baseline estimated error (RMS) is better than 5 cm.
Old survey locations can be found at Earls's website https://sites.google.com/site/ebfrederick/home